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We present a new characterization method for internal optical waveguide loss of blue, aquamarine, and green group-III–nitride laser diodes from as-grown wafers without need for further fabrication. This approach relies on excitation-position dependent polarization-resolved photoluminescence spectra collected from the edge of the planar waveguide. The high measurement accuracy of ±1 cm-1 enables for the first time determination of the mechanisms for p-layer optical loss from the waveguide loss difference before and after Mg dopant activation. Temperature-dependent measurements show that the dominant optical loss mechanism is absorption by acceptor-bound holes. This absorption mechanism does not depend significantly on light polarization.

We studied the effect of carrier population on light emission polarization of green InGaN quantum wells (QWs) on the semipolar ð11 22Þ plane. The 3 nm thick QWs emitting light at about 540 nm at low pumping power have electrical field (E) component E k ½ 1 123 stronger than that E k ½1 100. However, we found that increasing the pumping power changed the sign of the polarization ratio. Using the varied stripe length (VSL) method, we measured the optical gain for light propagating k½ 1 123 direction to be 2 times that of light propagating k½1 100 direction. We explain this behavior by inhomogeneous QW state filling.

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We studied the carrier transport phenomena of the multiple-quantum-well (MQW) active region and their impact on the performance of aquamarine and green laser diodes (LDs) grown on polar and semipolar planes. The ballistic carrier transport mechanism was found to be dominant in the MQW region. For the c-plane, because of the high hole capture probability and slow escape rate, mainly the quantum wells (QWs) positioned close to the p-side are electrically pumped. The optical loss induced by the underpumped QWs further away from the p-side leads to significantly higher laser threshold current density and a longer lasing wavelength with increased number of QWs. These effects are not significant for semipolar LD structures.